Add support for Nemotron Parse v1.2

[edknv]

Description

• Add support for Nemotron Parse v1.2 NIM, which no longer applies postprocessing server-side. Postprocessing is now handled client-side.
• Maintain backward compatibility with the old nemotron-parse:1.5.0 NIM.
• Update default NIM image to nemotron-parse-v1.2:1.7.0-variant.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• If adjusting docker-compose.yaml environment variables have you ensured those are mimicked in the Helm values.yaml file.